The elastomeric blend compositions of the present instant invention relate to compositions having improved physical and rheological properties for fabrication on conventional type fabricating equipment.
The blend compositions can be readily processed due to their superior rheological properties on conventional plastic fabrication equipment into elastomeric articles having excellent physical properties and desirable rubbery characteristics.
The hydroxyalkyl esters of this invention may be schematically represented as follows: ##STR1## wherein C is one or more carbon atoms in one or more molecules comprising a polymer and is in the polymer backbone chain of carbon atoms or is in an acyclic, alicyclic, or aromatic group which is pendant to the backbone chain; R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected from the group consisting of hydrogen, C.sub.1 to C.sub.18 straight and branched chain acyclic, alicyclic, aryl, alkylaryl, arylalkyl groups and functional derivatives thereof.
Products which have a limited concentration of ionic groups covalently bonded to one or more carbon atoms of one or more molecules comprising a polymer, when partially or completely neutralized with mono or polyvalent cations such as sodium, zinc, magnesium, lead, ammonium and quaternary ammonium compounds are generally referred to as ionomers. The ionic groups can be covalently bonded to carbon atoms comprising the backbone chain of the polymer, which chain of carbon atoms may be interrupted by hetero atoms such as oxygen, nitrogen and sulfur, or the ionic groups can be bonded to acyclic, alicyclic, or aromatic groups which are pendant to the backbone chain. Solid gel-free ionomers differ from covalently crosslinked elastomers, such as vulcanized rubber, in that while ionomers can be elastomeric at ordinary temperatures, at elevated temperatures they can be extruded, compression molded, blow molded, sheeted, vacuum formed and injection molded.
Sulfonated polymers i.e. those containing free sulfonic acid groups are known to be relatively unstable and are difficult to process in safety or without degradation in conventional plastic or rubber equipment at elevated temperatures. Except for this tendency to degrade it would be advantageous to process the free acid since the relatively weak ionic associations among the acid groups result in a low polymer viscosity permitting easy mixing with neutalizing agents, plasticizers, and other polymers. These systems can then be reacted with a neutralizing agent such as metallic oxides, hydroxides and alkoxides or salts of weak acids such as an acetate or stearate to yield the ionomer.
On the other hand, if the sulfonated polymer is first neutralized with a counterion and the ionomeric product isolated it is found to possess an extraordinarily high viscosity even at elevated temperatures commonly used for processing thermoplastic polymers in conventional equipment and must be mixed with other materials by solution techniques.
A major object of this invention is the preparation of low viscosity, thermally and hydrolytically stable esters of sulfonated polymers which are readily convertible to ionomers by reaction with a basic substance. A further object of this invention is the preparation of ionomers which comprises reacting a polymer having one or more sulfonic acid groups covalently linked or bonded to one or more carbon atoms in one or more molecules comprising said polymer with an oxirane to form a hydroxyalkyl ester, mixing the formed hydroxyalkyl ester with a wax and then reacting said formed ester with a basic substance selected from the group consisting of mono and polyvalent metallic oxides, hydroxides, alkoxides, and salts of acids having a lower K.sub.a than the sulfonic acid.
A further object of the present invention is to provide solid, gel-free blend compositions of a neutralized sulfonated polymer, a non-polar wax, and a hydroxyalkyl carboxylate ester, wherein the composition has improved processability on conventional fabricating equipment. These, and other objects of this invention will be further apparent in the detailed description of the invention which follows below.